Urba Centurion Update - (Kubota diesel, 100+ MPG in mixed driving - Fall 2012 on)

[GreenHornet]

Centurion #3 is generating quite the excitement on the East Side Maybe if I can generate half as much excitement out West together we may be able to convince a few to build Centurion #5 and #6

If anyone was going to deviate from the Centurion plans as it pertains to the transmission then I would have to say the clear cut choice would be a T5. I have thought about this for years and pondered tons of options. T5 is the lightest and strongest pound per pound. It also offers the most gearing options of any transmission that would be small enough in a Centurion or small car like Centurion. The tallest overdrive offered is a .63 compared to the .80 in the Samurai and .75 with the current Spitfire transmission and D type overdrive from the Volvo 1800. The other major advantage of the T5 is that you can get them anywhere they made tons of them. They are also relatively inexpensive and can be rebuilt by the average Joe.

Jack has done a wonderful job with Max and being that he is a fellow Oregonian I am very partial to the story. More Kubota powered cars on the road the better I say

GH..

[rustygirl]

GreenHornet you are right about the t5. Readily available and cheap is the way to go. I doodled with the gear ratios to see what we would get. See attached. I really like my Miata 6 speed in my Midget but it’s long, heavy, and required a great deal of modification to the tail housing. I would recommend against putting one in a Midget as it was a pain. The 6 speed ratios work well in the 1800 lb car however. A low 1st gear is important when power is low and with a redline of 3000 rpm, I try to shift at 2200, the gears shouldn’t be too far apart. In PA where I live it’s up hill, both ways. One regret from the GGP is not asking Jerry to trade cars for a bit. I’m curious how other Kubota powered cars drive.

The % to the right of the ratio is the difference between that gear and the one above it.

[changzuki]

GreenHornet & rustygirl,
The info in the transmission exchange is excellent, especially if anyone is deciding to build something with a Kubota mill. When GreenHornet is at a point where his is on the road we'll have even more data.
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IF I wasn't focused on freeway capable, the original Spitfire 1300 4 speed along with the 3.27 rear differential was a very nice and simple setup. 1st was low enough you could dump the clutch at idle and not stall the engine. 4th gear arrived quickly so shifting was mostly at a minimum. The drawback of course was a 65 mph limit against the governor making freeway driving somewhat worrisome.
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Currently (quirks aside) I do get a big kick out of the Spitfire 1500 transmission with overdrive. First is not as low as the older 4 speed but still not a problem even in town on inclines from a dead stop. The overdrive makes an excellent "patch" between 3rd and 4th and I use it often - especially where the speed limit is in the 30-35mph range. And the overdrive is very well suited to the 3.27 with this little D850 (65-70 cruise is not a problem).
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The real kick in the pants is the overdrive though. It shifts hard enough to remind me of an aggressive "shift kit" in an automatic, yet there is still the fun of manual shifting the regular gears. I will hate myself everytime there is a problem with it - but for the rest of the times - it is pure driving bliss that keeps a foolish grin visible.
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One thing I'll be interested in - mostly with GreenHornet's eventual setup - is the transition into the final gear at speed. With the D850, it's still quite a sensation to enter that top gear at a low rpm from an engine that just isn't making a lot of power at that point - but pulls like a train anyway. If there's a car dawdling along at 55-60mph and I need to move along I can. GreenHornet will hopefully give us a visual when the time comes and maybe it will have many reconsidering an engine of just two-cylinders!
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Thank you both for sharing your thoughts and info!!!!

~CrazyJerry

[changzuki]

Exhausting work!

While waiting for transmission parts, certain items on Centurion were revisited and a decision was made to try and improve on them.
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First on the list was the exhaust system. For all practical purposes, the standard exhaust on the Spitfire looks almost like it was an afterthought. The exhaust is generally the lowest point on these cars. Centurion's rocker panel is only 4.5 inches above the pavement - and the exhaust in spots is a bit lower and has scraped only a few times but it's always in the back of my mind when driving.
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Time to do something different~
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The following photo shows Centurion's the entire exhaust from the engine to rear bumper (see red line). This is now history.
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The replacement for this is much shorter, lighter, and is no longer the lowest point on the car (see green line)...
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Here's a comparison of the new exhaust next to the old muffler:
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On its own against the trailer shows in a little better:
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The whole assembly is about two-feet long.
Tucked in that two feet is a 9-inch glasspack.
Following it there's an additional tip with a perforated disc embedded inside to quiet it down to non-ticket levels.
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Where does it exit the car? From the photo below it should be real easy to spot!
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There's some important benefits to this new setup:
1) Cheap
2) Very simple
3) Very lightweight
4) Elimination of a major undercarriage heat source
5) Which enables the use of a full bedliner belly pan with no danger of melting
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I may be done for now - but trust there is more coming very soon!
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~CrazyJerry

[GreenHornet]

Great idea CJ

Let us know how much weight this cut out I am super curious
and of course how it works once its all dialed in.

I was thinking about something similar but venting it underneath the car. I was just concerned about the exhaust fumes potentially getting inside the cabin if the windows are opened. Hopefully you will not experience this problem.

looking forward to your feedback and results,

GH..

[changzuki]

Originally Posted by GreenHornet

Great idea CJ

Let us know how much weight this cut out I am super curious
and of course how it works once its all dialed in.

I was thinking about something similar but venting it underneath the car. I was just concerned about the exhaust fumes potentially getting inside the cabin if the windows are opened. Hopefully you will not experience this problem.

looking forward to your feedback and results,

GH..

Hi GreenHornet!
The full exhaust that was removed was only 28 pounds.
The replacement unit is a just a bit over 7 pounds. It's easily removable in a few minutes and the car doesn't need to be raised. The muffler itself and the internal baffle are both replaceable - also without raising the car. There's not the slightest hint of exhaust fumes in the cabin even during traffic light stops. Best of all, it can't scrub the ground.
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This is getting a little ahead of the next few posts, but performance-wise the Kubota is responding wonderfully with it. Nothing was lost on the upper or lower rpm ends. I tried using course steel wool to quiet it down but it simply didn't last, so the perforated disc was added. So far the disc is holding up well and can also be removed in a couple of minutes if necessary.
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It took a pile of self-control to route it towards the ground. The world will never know how badly I wanted a stack!
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~CrazyJerry

[changzuki]

Funyuns and Trunnions!
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Many folks have heard of "Funyuns" but not as many have heard of "Trunnions". Triumph (and some other early cars) did use a ball joint in the upper part of their front suspension, but did not use a lower ball joint. Instead, they used something called a trunnion. This trunnion allowed the front suspension to move up and down (over road bumps, etc) while helping the tire tread to stay true to the road surface. It also allowed for the front wheels to steer left and right around its lower pivot point.
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Like ball joints, trunnions can, and do, wear out. And like ball joints, sometimes they break! When this happens the front wheel usually goes up into the fender and the front of the car slams down to the road :
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The trunnions on this Centurion are indeed the originals from 1966! It was time to replace them and as luck would have it, there is a new design that will do away with the trunnions forever! To replace them required removal of the front wheel:
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The trunnions (and vertical link they are attached to) can be seen from behind:
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And once removed we can see very clearly, the vertical link and the trunnion:
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To understand why they sometimes fail with no warning, we need to look a bit closer.
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Notice in the photo below that the brass trunnion on the right threads onto the vertical link:
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And if we unscrew the trunnion all the way it will of course be free from the vertical link. As you look at this photo, notice the threaded vertical link is drilled up through the center. This hole is supposed to provide a path for oil to flow downward into the trunnions when it is serviced (lubed). The oil that is down in the trunnions is then supposed to wick up the onto the threads and help keep this assembly from prematurely wearing out. The drilled hole also presents a problem. The material that was removed in the drilling process has also made the part weaker. In addition, all those threads used to hold it together, has also made the part weaker:
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It has also been said that rust can form beneath the protective rubber rings that were designed to keep debris from getting in. Looking beneath that rubber ring there is some rust starting.
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When the vertical link fails, it will break at the weakest point which may be either at the threaded area or at a bad rust scored area. And this is a photo of a failed vertical link:
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The new design specifically to eliminate this problem uses a vertical link that is not drilled so it is stronger than the original:
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And the trunnion is now replaced by a simple heim joint:
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Now that we all up to date with the Trunnions, wouldn't you rather have just dealt with the Funyuns?
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~CrazyJerry

[GreenHornet]

Originally Posted by changzuki

Hi GreenHornet!
The full exhaust that was removed was only 28 pounds.
The replacement unit is a just a bit over 7 pounds. It's easily removable in a few minutes and the car doesn't need to be raised. The muffler itself and the internal baffle are both replaceable - also without raising the car. There's not the slightest hint of exhaust fumes in the cabin even during traffic light stops. Best of all, it can't scrub the ground.
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This is getting a little ahead of the next few posts, but performance-wise the Kubota is responding wonderfully with it. Nothing was lost on the upper or lower rpm ends. I tried using course steel wool to quiet it down but it simply didn't last, so the perforated disc was added. So far the disc is holding up well and can also be removed in a couple of minutes if necessary.
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It took a pile of self-control to route it towards the ground. The world will never know how badly I wanted a stack!
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~CrazyJerry

Another thing I noticed while looking at my Centurions undercarriage today was just how much potential there is for a deeper trunk space with the rear exhaust and muffler delete. Extending that down and shaping it aerodynamically would help MPG potential I think. You could also create attachment points for the mid area panels to attach this would make for a cleaner and smoother look.

CJ do you think there would be any negatives to exiting underneath the vehicle vs to the side with a shorty exhaust?

[UltArc]

Adding trunk space?!?! Run the exhaust into the wake!!!

[changzuki]

Originally Posted by GreenHornet

Another thing I noticed while looking at my Centurions undercarriage today was just how much potential there is for a deeper trunk space with the rear exhaust and muffler delete. Extending that down and shaping it aerodynamically would help MPG potential I think. You could also create attachment points for the mid area panels to attach this would make for a cleaner and smoother look.

CJ do you think there would be any negatives to exiting underneath the vehicle vs to the side with a shorty exhaust?

Well, on the first point (rear tray) the one on mine isn't going downward much more than it is right now. There's not a clear path to lower the floor of it like yours may have. Instead, there is a very sturdy battery tray back there:
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And lastly, looking up from underneath:
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Not knowing how the overall weight distribution would translate to real world driving I decided to leave that piece in place.
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Good question about the exhaust GreenHornet. I'll bet there are plenty of ideas bouncing around about this. In the quest to eliminate the full exhaust system, I did have an undercar exit as you suggest. This didn't last long - me personally - I hated it.
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The main reason was the resonant noise from the sound waves bouncing off the road and through the various cavities under the car. The cabin noise wasn't deafening - it just had an undesirable tone, and with no real sound deadener to muffle it, well, it had to be routed elsewhere. To ensure the exhaust was not the low point under the car meant the pipe ended at least level with the boxed frame members upfront. A similar scenario played out when the exhaust exited in the front wheel well itself, and I hated that too.
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Victory was achieved once I got out just past the lower fender - and from in the cockpit, it was like a symphony to my ears (but it still may not be for everyone.)
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~CrazyJerry
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